To save a shape or path as a custom shape:
In the Paths palette, select a path--either a vector mask for a shape layer, a work path, or a saved path.
Choose Edit > Define Custom Shape, and enter a name for the new custom shape in the Shape Name dialog box. The new shape appears in the Shape pop-up palette.
To save the new custom shape as part of a new library, select Save Shapes from the pop-up palette menu.
You can also use the Preset Manager to manage libraries of custom shapes. For more information, see Managing libraries with the Preset Manager (Photoshop).